Berserker is Frankenstein, Frankenstein's monster, the homunculus created by Victor Frankenstein appearing in Mary Shelley's novel. Into the Great Holy Grail War Berserker is summoned by Caules Forvedge Yggdmillennia with Victor Frankenstein's plans for a "perfect human" as a catalyst

Spoiler

Berserker's True Name is Frankenstein (フランケンシュタイン, Furankenshutain), the Frankenstein's monster (フランケンシュタインの怪物, Furankenshutain no Kaibutsu). Based upon the artificial life created by Victor Frankenstein in Mary Shelley's novel "Frankenstein: or the Modern Prometheus". Victor sought to recreate the original couple described in the bible -- Adam and Eve. Due to the limitations of man, he first built Eve, intending for her to give birth to the counterpart. What started as a patchwork of lifeless flesh was given life by the energy harnessed from lightning. Unfortunately, what awoke was not the ideal woman that Victor envisioned, but an abomination with the mind of an infant. Having no developed capacity for expression, her sense of morality was completely absent. After presenting the entrails of a slain dog as a gift for the master, she was branded a failure and disassembled, before being abandoned completely.